Centrifugal impellers



United States Patent CENTRIFUGAL INIPELLERS Application February 28, 1951, Serial N 0. 213,144

Claims. (31. 103-115 This invention relates to centrifugal impellers of the character employed in pumps, injectors and the like.

When centrifugal impellers, whether used in pumps or as injectors, and the like, are designed to handle low fluid flows at large pressure heads and at low speeds of rotation, the width of the discharge gap and the mean height of the impeller vanes becomes quite small. By reason of these considerations the efficiency of such impellers is inherently low. However, if such impellers are designed and manufactured in the conventional ways they are as costly and as troublesome to make as the impellers of inherently high efliciencies.

I have found that these inherently low efnciency impellers can be made more simply and cheaply than heretofore without materially lowering their efiiciency.

It is the principal object of this invention to provide a centrifugal impeller, characterized by its narrow discharge gap and the low mean. height of its vanes, of f simple and rugged construction which can be simply and easily manufactured at low cost and whose eificiency compares favorably with the conventional impellers of this type. I

It is also a principal object of this invention to provide a centrifugal impeller whose disc, vanes, and shroud are made separately by simple operations and subsequently assembled and formed into an operating unit by screws or similar fastening means, said vanes being formed from stock of wedge cross-section and being of a material suficiently deformable when pressed by said disc and shroud, through said fastening means, to assume the contour of the fluid passageway, said fastening means being such as to accurately space said shroud from said disc.

It is a further important object of this invention to provide a centrifugal impeller Whose vanes are formed separately from the disc and shroud thereof, said vanes being formed from stock of wedge cross-section by a simple operation and being of a synthetic deformable plastic material.

The further objects, features and advantages of the invention will be apparent from a consideration of the following detailed description of a present preferred embodiment thereof taken with the accompanying drawings, in which: i I Fig. 1 is a cross-sectional view of a centrifugal pump provided with the novel impeller of the invention;

Fig. 2 is a sectional view taken on line Z2 of Fig. 1

showing the impeller disc with some of' the vanes in po- 2,780,176 Patented Feb. 5, 1957 by reason of the conditions of operation, high efiiciencies are inherently unobtainable. In the latter cases the novel impeller while it may not provide efficiencies higher than those obtainable by conventional impellers will provide efl'iciencies of the same order as those of conventional impellers.

' The pump 10 is an example of the latter case and has been designed to handle low fluid flows at large pressure 7 heads and at low speed of rotation of the impeller.

The pump 10 includes a two part casing 11 held together by a circular series of 'bolts 12. The peripheral portions of the halves of the casing 10 are shaped to provide the outlet scroll 13 of theusual sort. The casing 10 includes an extension 14 which carries the bearing 16 for the impeller shaft 17 which may be driven by any of the usual means, not shown. For convenience the shaft 17 is made hollow so that it also serves as the pump inlet means.

The shaft 17 carries integral therewith the impeller disc 18, which alternatively may be separately formed and united in any preferred manner to the hollow shaft 17. The disc 18 may be formed by a casting or a forging operation, as preferred, and the fluid passageway defining face '19 thereof finished by a simple machining and/ or grinding operation. It is to be noted that since the vanes 20' are not integral with the disc 18 and do not extend from the face 19, said face is an uninterrupted surface of revolution generated by the rotation of a line about the axisof the shaft 17 as a center and may be machined or ground as by rotating it in a lathe against a tool or grinding wheel. The shroud disc 28 may also be formed by a casting or forging operation, as preferred, and the fluid passageway defining face 30 thereof finished by a simple machining and/ or grinding operation. It is again to be noted that the vanes 20 are not integral with the shroud 28 and do not extend from the face 30, hence said face is also an uninterrupted surface of revolution generated by the rotation of a line about the axis of the shaft 17 as a center and may be machined or ground as by rotating it against a tool or a grinding wheel. The shroud 28 includes a central portion 31 that extends intothe hollow of the shaft 17. The vanes 20, as best shown in Figs. 2 and 3, approximate an airfoil in shape and curve from their wider inlet ends to their narrower outlet ends so that said out let ends are at a considerable angle to the radius of the impeller and with the impeller disc 18 and theshroud disc 28 define a series of like shaped passageways for the fluid handled.

It is to be noted that in accordance with the design vanes 20 is quite small and the change in height of the vanes 20 is gradual and approximates a straight line function. Thus, the vanes 20, if made of a material that is sufiiciently deformable, may be formed as fiat wedge material.

elements of proper taper and shaped to the proper contour by pressing them, in their final location, between the disc 14 and the shroud 28. The vanes 20 may be made of deformable metal such as aluminum and lead, and their alloys, or they may be made of synthetic plastic available with corrosion resistance properties superior to those of the common metals-and is easy to form and.

shape.

The vanes 2i) may conveniently be formed from stock of the proper taper, as for instance the wedge block 33,

of plastic material, by a simple operation such as'sawing, punch pressing, etc., which does not require hand .finishing. The holes 35 may be formed in the vanes 20 separately or as part of the punching operation when At present it is preferred to form the vane 20- of synthetic plastic material as such material is readily.

said operation is employed. When the vanes are formed of plastic material they are made of somewhat greater height than the design height and the areas 37 of the face 19 and/or the'face 30,- ultimately covered by the vanes 20, provided with'shallow holes 39, or shallow grooves, or are checkered, so as to receive material of the vanes20 to lock them to the disc 18 and/ or the shroud 28.

The disc 18 is provided with a pair of counter-sunk holes 40 while the'shrou-d 28 is provided with a pair of tapped holes 41 for each vane 20'employed. Each pair of disc holes 40 is adapted to' register with a pair of vane holes and a pair of shroud holes 41 when the impeller 11 is assembled. Each hole 41 is countersunk to provide a fiat bearing surface 43 accurately located relative to the portion of the surface 30 around it. Each shoulder 45 is also accurately located relative to the portion of the surface 19 around its hole and provides a bearing surface accurately located relative to the portion of the surface 19 around its hole 40. Each set of aligned holes 40, 35 and 41 is adapted to receive a screw 47 which includes a straight shank portion 48.

The length of the shank 48 of the inner series of screws 47 is longer than that of the outer series of screws 47. The

shanks 48 of the screws 47 of each of said series are accurately cut to length, the shank lengths chosen being such that when the screws 47 are driven home in their espective holes 41 and the shoulders formed at the end of the shanks 48 adjacent the threaded portions of the screw 47 are snug on the horizontal bearing surfaces 43, while the opposite ends of the shanks 48 are in line with the bearing surface of the shoulders the disc 18 and the shroud will be accurately spaced from each other and the vanes 20 will all be brought to the designed height throughout their'lengths. To facilitate this operation the disc 14 and the shroud 28' may be heated to render the plastic vanes 20 sufiiciently plastic to readily deform. If the vanes 20 are of metal then only a minimum thinning thereof can be anticipated so that they must initially closely approximate their design height.

I claim:

1. A centrifugal impeller comprising a rotatable shaft, a disc member extending from said shaft and rotatable therewith, a shroud member spaced from said disc member and centered to rotate therewith, said members pre senting opposed fiow path defining surfaces, said defining surfaces each being a surface of revolution generated by the rotation of a line about the axisflofsaid shaft as a center, a plurality of vanes dividing the space between said defining surfacesinto a plurality of'like fiow' passageways, said vanes each having a plurality of spaced holes therethrough, said members each having'aplural ity of holes therein, each of the disc holes and each of the shroud holes being aligned with arespective one ofsaid vane holes, one hole of each aligned pair of'discholes and shroud holes'being tapped with one end thereof opening at its respective one of said defining surfaces,

material around said one end being removed toqprovide a bearing surface predeterminately positioned relative to its surrounding defining surface, the other hole of each aligned pair of disc holes and shroud holes being stepped, the bore of said stepped hole of smaller diameter opening at its respective oneof said defining surfaces and extending into its one of said members a predetermined distance, the bore'of larger diameter meeting said bore of smaller diameter and opening at the outer surface of its one of said members, a plurality of connecting members adapted to enter the aligned holes of said shroud member, said disc member and said vanes, said members each including a tool engaginghead portion of a diameter to fit into said bore of larger diameter, a shank portion of predetermined length adapted tofit in said smaller bore and the hole in the respective vane and terminat high a shoulder'adaptedto' bear on said bearing surface,

and a threaded portion of reduced diameter extending from said shoulder and adapted to be screwed into said tapped hole whereby when said connecting members are screwed into said tapped holes as required to seat said shoulders on said bearing surfaces and said head portions on the ends of said large diameter bores, said defining surfaces are predeterminately spaced throughout.

2. In the method of forming a centrifugal impeller including a rotatable shaft, a disc rotatable with said shaft, and a shroud spaced from said disc by vanes formed of a material more easily deformable than the materials of said disc and said shroud, said shroud adapted to be connected to said disc for unitary rotation, said disc and shroud presenting spaced opposed flow path defining surfaces each generated by the rotation of a line about the axis of said shaft as a center, the steps comprising positioning a plurality of separately formed substantially fiat, stifi flow path defining vanes between said disc and said shroud, distributing said vanes to divide the space between said disc and said shroud into a plurality of like flow passageways, connecting said shroud and said vanes to said disc and exerting pressure on said vanes through said disc and said shroud to deform said vanes to the contour of said defining surfaces covered by said vanes.

3. In the method of forming a centrifugal impeller including a rotatable shaft, a disc rotatable with said shaft, and a shroud spaced from said disc by vanes formed of a material more easily deformable than the materials of said disc and said shroud, said shroud adapted to be connected to said disc for unitary rotation, said disc and shroud presenting spaced opposed flow path defining surfaces each generated by the rotation of a line about the axis of saidshaft as a center, the steps comprising positioning a plurality of separately formed substantially fiat, stiff flow path defining vanes of greater mean height than the ultimately desired mean spacing between said disc and said shroud between said disc and said shroud, distributing said vanes to divide the space between said disc and said shroud into a'plurality of like fiow passageways, passing connecting members through said disc, said vanes and said shroud, applying pressure on said disc and said shroud through said connecting members to move said disc and said shroud toward each other and simultaneously deforming said' vanes by the pressure'exerted thereon by. said disc and said shroud-to reduce the mean height'of said vanes, and continuing said pressure application until said disc and said shroud attain a predetermined spacing and the mean height of said vanes is reduced to a predetermined ultimate mean height.

4. In the method of forming a centrifugal impeller including a rotatable shaft, a disc extending from said shaft, and a shroud spaced from said disc by vanes formed of a non-metallic plastic material more easily deformable than the materials of said disc and said shroud,

" said shroud centered to rotate with said disc, said shroud and said disc presenting opposed flow path defining surfaces each generated by the rotation of a curved line about the axis of said shaft as a center, the steps comprising positioning a plurality of separately formed, fiat stiff flow path defining vanes of wedge cross section between said disc and said shroud, distributing said vanes to divide the space between said disc and said shroud into a plurality of like flow' passageways, securing said disc, said shroud and said vanes together as a unit and during said securing step applying sufficient pressure on said vanes through said disc and said shroud to deform said vanes to the curved contour of said defining surfaces covered by said vanes. I

5. The method setforth in claim 4 wherein prior to the positioning of said vanes between said disc and said shroud, the portions of said disc and said shroud ultimately covered by said vanes are removed to provide shallow References Cited in the file of this patent UNITED STATES PATENTS Kreher July 9, 1912 Dickinson July 20, 1920 6 Kennedy Sept. 29, 1931 Allen July 17, 1934 Salerni Aug. 25, 1942 Troxler Nov. 1, 1949 Bolender Apr. 4, 1950 FOREIGN PATENTS Great Britain Oct. 27, 1927 

